Powered by a 1,600shp (1,1190kW)-class turbine engine, the design is 20% larger and 50% heavier than the Israeli company's standard Mule UAV. The new version has been designed in response to a US requirement for a high-speed unmanned cargo delivery capability, says Urban Aeronautics president Rafi Yoeli.

Data gathered during the recent windtunnel test, conducted in the USA using a subsonic facility at Penn-State University, shows that the aircraft is capable of exceeding its 250kt performance target, Yoeli says.

Urban says the larger design's performance comes mainly through the stagger that is built into its three main components: forward fan, centre fuselage and rear fan. It also has a horizontal stabiliser mounted at the rear of the vehicle and canted sharply upwards.

While in the hover the fans are essentially horizontal to the ground, and the UAV's vane control system and other company-patented aerodynamic and flight-control provisions enable it to take advantage of the standard Mule design's advantages in terms of safety, gust resistance and noise, the company says.

When in forward flight, the whole vehicle tilts forward so that the lift fans are acting partly as thrusters. Lift is shared between the fuselage, which takes most of the burden through a specially designed shape that interacts aerodynamically with the incoming flow and the two ducted fans, and the horizontal tail. Additional lift comes from the fans themselves.

It remains to be seen whether Urban will start full-scale development of the new high-speed variant, as all its efforts are now focused on the more compact, lower cost and mechanically simpler Mule. A prototype of the baseline vehicle should start hover tests in the coming weeks.